Over the last year, our studies have been concerned predominantly with the characterization of cytoskeletal proteins in chronic lymphocytic leukemia (CLL) lymphocytes. Previous studies from this laboratory have shown that actin is a major protein of human lymphocytes. We now report the purification to homogeneity and characterization of actin from blood lymphocytes of normal subjects and patients with CLL. The possible significance of the observed differences between the myosin Mg++-ATPase activation by CLL and normal lymphocyte actin has been investigated. Studies have been initiated on vimentin, the major protein of intermediate filaments, and its role in normal and CLL lymphocytes. Over the next year, we will again focus on 5' nucleotidase (5'N). Specifically, the induction of 5'N in 5'N negative CLL lymphocytes by TPA (4-beta-phorbol 12-betamyristate 13-alpha-acetate) will be investigated. These investigations will continue our longterm documentation of similarities and differences between normal and CLL lymphocytes.